This invention relates to vehicle steering column assemblies and more particularly to length-adjustable shafts for use in such adjustable steering column assemblies and methods of constructing length-adjustable steering column assemblies.
Steering column assemblies which are adjustable axially (reach adjustable) normally include an inner steering column member mounted in an outer steering column member, the two column members being relatively slidable to allow for the axial adjustment. Normally, the inner and outer steering column members are of non-circular cross section to transmit torque between them, and a triangular configuration is common. To inhibit vibration between the two members, it is common to mount a bush between them, so that one can slide relatively to the other. It is common practice for the bush to be pressed on, or to be permanently fixed by staking or by other means on the inner steering column member. The combination of the bush and inner steering column member is then designed, by close tolerance between the outer form of the bush and the inner form of the outer steering column member, to slide, thus allowing the required axial adjustment.
Problems associated with this are that the outer steering column member, which is tubular in the region of the bush, must be parallel over a length sufficient to cover the length of the bush and also the length of the axial adjustment stroke. All three components, therefore, have to be accurately controlled for dimensional tolerance, which is costly, especially for components with non-circular cross sections, and, in addition, there will always be a clearance required for manufacturing tolerances. This will result in a potential backlash and xe2x80x9cchucklexe2x80x9d, i.e. axial rock of the inner column member in the outer.
The foregoing illustrates limitations known to exist in present telescopic shafts for use in adjustable steering columns. Thus, it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the present invention, this is accomplished by providing a vehicle steering column assembly comprising an inner column member mounted in an outer column member, the two column members being relatively slidable to allow axial adjustment of the steering column; and a bush mounted with a sliding fit on the inner member inside the outer member, said bush being fixed within said outer member.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.